Hand-polished aircraft-grade aluminum is used almost exclusively in XTR speakers because few materials are rigid and resonance-free enough to perform well in compact sizes. With a patented XTDD anodized aluminum dome driver and pure aluminum dome tweeter‰ۡóÁÌÎ?ÌÎÌÕthe same found in larger XTR speakers‰ۡóÁÌÎ?ÌÎÌÕthe XTR 40 offers an incredibly broad sound experiences with a sleek, modern profile design to match.